1. Field of the Invention
The invention relates to altitude determining devices and more particularly to an optical range finder which receives light reflected from a surface and produces signals indicative of the range to the surface.
2. Description of the Prior Art
In the prior art, optical range finders have employed a pair of spaced, photosensitive devices having output parameters which vary as a function of the magnitude of light reflected from an object and falling on the devices. Comparison of the parameters from each device is used to determine the angle of incidence of the reflected light and, thereby, the distance from the object to the devices. At short distances the relative sensitivity of such devices is high. At greater distances, however, the dispersion of reflected light incident upon the photodetectors is diffused, thereby lowering the sensitivity of such devices significantly.